Block filter



FIG. 1 is a front perspective view of the block filter embodying the new design;

FIG. 2 is a front elevational view thereof; the rear elevational view being the same as FIG. 2;

FIG. 3 is a left side elevational view thereof; the right side elevational view being the same as FIG. 3;

FIG. 4 is a bottom plan view thereof; and,

FIG. 5 is a top plan view thereof. 

The ornamental design for a block filter, as shown and described. 